Known projector barrels for shell launchers are closed at the lower end thereof by a closure cap and include a breech ring which is substantially spherical in shape. The breech ring is used to engage a base plate which lies on the ground and is secured against slippage by a structure such as ribs formed thereon. The recoil of such projector barrels can be comparatively well absorbed when shells are fired with the barrel engaged with such a base plate. It has been found that such recoil may be absorbed even with projector barrels having a fairly large caliber as in the case of 120 mm.
Such shell launching assemblies are relatively easy to operate and to transport. With barrels having heavy calibers such as 120 mm., shell launching assemblies using the base plate produce comparatively large recoil forces which are immediately absorbed by the base plate. When mounting shell launching assemblies for smaller caliber barrels on the loading surface of a vehicle, the base plate is connected directly to such loading surface. In this instance, the substructure of the vehicle must be appropriately reinforced because of the absorption of the recoil forces.
However, it has been found impractical to mount shell launching assemblies of larger caliber projector barrels in this way onto a vehicle because of the type of construction necessary and the related expense. For example, the recoil forces of a 120 mm. caliber projector barrel may attain from about 100 to 160 tons. Even with a specific reinforcement of the substructure, conventional vehicles are not able to absorb such forces. Furthermore, the construction of such a vehicle is simply not cost effective.